While washing my 84 300D I noticed debris coming from the base of the C Pillar. Spraying water behind this fin washes a never ending supply of dark brown material out of the holes that the drain the rear of the sunroof. It looks like some kind of degraded sponge like material. I tried to get it all washed out but it just keeps coming. After letting this debris dry, it is crispy and crumbles. Does anyone know what this is?